Fuel cutoff circuit responsive to engine deceleration conditions for use in conjunction with the fuel delivery system for an internal combustion engine

ABSTRACT

A circuit is disclosed which includes a Schmitt trigger having a pair of control electrodes and which is responsive to a plurality of engine conditions to generate an output signal when the engine conditions indicate that a termination of fuel delivery to the engine is necessary. The circuit is preprogrammable to generate an output signal when the engine speed is in excess of a preselected value and a selected switch has changed state and to thereafter continue to generate the output signal while the switch state remains constant and until engine speed drops to a second, lower, preselected value.

United States Patent 11 1 Luchaco [451 May 7, 1974 1 FUEL CUTOFF CIRCUITRESPONSIVE TO [75] Inventor: David G. Luchaco, Horseheads,

[73] Assignee: The Bendix Corporation, Southfield,

Mich.

[22] Filed: v Sept. 27, 1971 [21] Appl. No.: 183,907

[52] US. Cl. 123/32 EA, 123/119 R, 123/97 B [51] Int. Cl. F02m 51/00[58] Field of Search 123/32 EA, 119 R [5.6] References Cited UNITEDSTATES PATENTS 3,463,130 8/1969 Reichardt et al 123/32 EA 12/1971Grossclaude 123/97 B Primary Examiner-Laurence M. Goodridge AssistantExaminer-Cort Flint Attorney, Agent, or Firm.Gerald K. Flagg; Robert A.Benziger 57' I ABSTRACT A circuit is disclosed which includes a Schmitttrigger having a pair of control electrodes and which is responsive to aplurality of engine conditions to generate an output signal'when theengine conditions indicate that a termination of fuel delivery to theengine is necessary. The circuit is preprogrammable to generate anoutput signal when the engine speed is in excess of a preselected valueand a selected switch has changed state and to thereafter continue togenerate the output signal while the switch state remains constant anduntil engine speed drops to a second, lower, preselected value.

3,483,851 12/1969 Reichardt 3,570,460 3/1971 Rabus 123/32 EA 2 Claims, 4Drawing Figures TO TRANSMISSION 304 PARK OR NEUTRAL SWITCH 356 Gambill123/32 EA PATENTEUHAY 7 I974 SHEET 1 UF 3 \|&

TEMPERATURE SENSOR BATTERY ELECTRONIC o TIMING CONTROL PICKUP UNITFIGURE DAVID e. LUCHACO INVENTOR.

PATENTEDHAY 7 m4 3,809,028

SHEET 2 UF 3 FIGURE 2 DAVID e. LUCHACO- INVENTOR.

PATENTEDHAY 7 m4 SHEET 3 [IF 3 MERE m mmDwl DAV I D G. LUCHACO INVENTOR.

FUEL CUTOFF CIRCUIT RESPONSIVE TO ENGINE DECELERATION CONDITIONS FOR USEIN CONJUNCTION WITH THE FUEL DELIVERY SYSTEM FOR AN INTERNAL COMBUSTIONENGINE CROSS REFERENCE TO A RELATED APPLICATION This is related to myco-pending commonly assigned patent application Ser. No. 193,824 ACircuit for Controllably Driving a Schmitt Trigger in Response toPreselected Variations in an Analog Input Signal and in a DigitalizedInput Signal filed on Oct. 29, 1971 as a division hereof.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to the field of electronic fuel control systems forinternal combustion engines and more particularly to that portion of theabove-noted field which relates to intermittent duty circuits formodifying or altering a fuel delivery pattern. In particular, thepresent invention relates to that portion of the above-noted field whichis concerned with circuits for terminating delivery of fuel to an enginein the presence of selected deceleration conditions.

2. Description of the Prior Art The prior art as represented by US. Pat.No. 3,570,460, issued Mar. 16, 1971, to Friedrich Rabus, illustrates acircuit for terminating fuel delivery to an engine upon theoccurrence'of two conditions; namely, closing of the air consumptioncontrolling throttle and vehicle engine speed in excess of a firstpreselected value. This is achieved by strongly biasing a transistorinto its nonconducting or off region so that a second transistor whichis controlled thereby is strongly biased into the conducting or oncondition to an extent that it may not be switched off. Switching off ofthis second transistor is necessary for the generation of an injectioncommand. Once the first transistor is strongly biased off, thattransistor is held off until the engine speed drops to a secondpredetermined value. Both speed signals are generated by integrating apulse frequency through a resistive-capacitive network and-thereafterapplying the average voltage at one portion of that network to thecontrol electrode of the first transistor. This bias must have obtaineda first value in order to strongly bias the first transistor off andcross coupling with the collector of that transistor further accentuatesthe bias value. As the engine speed decreases, the integrated signalfollows the speed decrease and the bias applied to the first transistorcontrol electrode gradually changes to a point where the transistor isno longer strongly biased off. This then represents the second, lower,selected engine speed. The throttle position input is derived byestablishing a strong on bias for the first transistor control electrodeduring open throttle position and by subsequently shorting out this biasto ground by closure of a grounded contact whenever the throttle isclosed. Thus, both the high and low speed input signals and the throttleposition signal are applied to the control electrode of the firsttransistor as noted above.

The approach of this patent contains three operational flaws whichrender it undesirable in use. Firstly,

by generating both the high and low speed signals with the samecollection of electrical elements, one cannot easily modify the high rpmpoint without concomitantly affecting the low rpm point. Thus, tailoringof the circuit to suit differentengine applications becomes verycomplicated and expensive. Secondly, while the integrating technique forthe high rpm point produces reasonably accurate results, use of theintegrating technique to establish the low rpm point requires that thecircuit be adjusted for a relatively high value of rpm, since theintegrating circuit will have a slow response and the voltage signalwill lag somewhat behind the actual engine speed. Since the low rpmpoint at which fuel delivery is restarted must be sufficiently high sothat the engine will not stall out, the established low rpm speed mustbe somewhat higher than the desired speed. Thirdly, the technique whichrequires the turning off of electronic elements, while theoreticallyequivalent to the turning on of electronic elements, presents someproblems in the practical aspects in that the interrelation of thevarious elements may not present a level of voltage which issufficiently low to accomplish the desired turn-off effect, while atechnique which contemplates the turning on of the electronic devicesis, in a practical sense, easier to accomplish. In view of the foregoingproblems discussed in relation to the above-noted United States LettersPatent, it is an object of the present invention to provide a circuitfor generating a fuel cutoff signal during selected periods of enginedeceleration which is readily tailorable for different engineinstallations. It is a further object of the present invention toprovide such a circuit having a fast response time at low engine rpmoperation. It is a still further object of the present invention toprovide a circuit of the above-noted type in which the low speed sensingis accomplished substantially within one cycle of operation. It is astill further object of the present invention to provide a systemof theabove-noted type in which speed sensing is accomplished on apulseto-pulse basis.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of anelectronic fuel control system adapted to a reciprocating pistoninternal combustion engine.

FIG. 2 shows, in diagrammatic circuit form, an electronic fuel controlsystem main computing means including a variable frequency, fixedduration pulse generator for use in the present invention.

FIG. 3 shows, in diagrammatic circuit form, the fuel cutofi' circuit ofthe present invention responsive to engine deceleration commands over.certain engine speed ranges.

FIG. 4 shows an alternative input portion for the circuit of FIG. 3 foruse when the source of input signal is of comparatively low energy orvoltage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG.1, an electronic fuel control system is shown in schematic form. Thesystem is comprised of an electronic control unit, or computing means10, a manifold pressure sensor 12, a temperature sensor 14, an inputtiming means 16, and an additional sensor, such as an air temperaturesensor, de-

noted as 18. Temperature sensor 14 may sense engine temperature directlyor indirectly, or may also sense injection stream temperature directlyor indirectly. The

manifold pressure sensor 12 and additional. sensor 18 are mounted onthrottle body20. The output; of thecomputing means is coupled to anelectromagnetic injector valve member 22 mounted in intake manifold 24and arranged to provide fuel from tank 26 via pumping means 28 andsuitable fuel conduits 30 .for delivery to a combustion cylinder 32 ofan internal combustion engine otherwise not shown. While the injectorvalve member 22 is illustrated .as delivering a spray of fuel toward anopen intake valve 34, it will be understood that this representation ismerely illustrative and that other delivery arrangements are known andutilized.

' Furthermore, it is well known in the art of electronic fuel controlsystems that computing means 10 may control an injector valve meanscomprised of one or more Referring now to FIGS. 1 and 2 and particularlyto FIG. 2, an electronic fuel control system main computation circuit110 is shown. The circuit is shown as being energized by a voltagesupplydesignated as B+ at the various locations noted. In theapplication of this system to an automative engine fuelcontrol system,the

voltage supply B+ could be the battery 36 and/or battery charging systemconventionally used as the vehicles electric power source. The manskilled in the art will recognize that the electrical polarity of thevoltage supply could be readily reversed.

The circuit 110 receives, along with the voltage supply, various sensoryinputs, in the form of voltage sig nals in this instance, indicative ofvarious operating parameters of the associated engine. Intake manifoldpressure sensor 12 supplies a voltage indicative of man'- ifoldpressure, temperature sensor 14 is operative to vary the voltage acrossthe parallel resistance associated therewith to provide a voltage signalindicative of engine temperature and voltage signals indicative ofengine speed are received from input timing means 16 at circuitinputport 116. This signal may be derived from any source indicative ofengine crank angle, but is preferably from the engines ignitiondistributor (not shown).

The circuit 110 is operative to provide two consecutive pulses, ofvariable duration, through sequential networks to circuit location 118to thereby control the on time of transistor 120. The first pulse isprovided via resistor 122 from that portion of circuit 110 having inputsindicative of engine crank angle and intake manifold pressure. Thetermination of this pulse initiates a second pulse which is provided viaresistor 124 from that portion of the circuit 110 having an input fromthe temperature sensor 14. These pulses, received sequentially atcircuit location 118, serve to turn transistor 120 "on" (that is,transistor 120 is triggered into the conduction state) and a relativelylow voltage signal is present at circuit output port 126. This port maybe connected, through suitable inverters and/or amplifiers to theinjector valve means (shown in FIG. 1) such that the selected injectorvalve means are energized whenever the transistor is on" and the lowlevel signal appears at output port 126. It is the current practice touse switching means to-control which of the injector valve means arecoupled to circuit port 126 when the system is used for actuation-ofless than all injector valve means at any one time. Because the injectorvalve means are relatively slow acting, compared with the speed ofelectronic devices, the successive pulses at circuit point 118 willresult in the injector valve means remaining open until after thetermination of the second pulse.

The duration of the first pulse is controlled by the monostablemultivibrator network associated with transistors 128 and 130. Thepresence of a pulse received via input port 116 will trigger themultivibrator into its unstable state with transistor 128 in theconducting state and transistor blocked (or in the nonconducting state).The period of time during which transistor 128 is conducting will becontrolled by the voltage signal from manifold pressure sensor 12.Conduction of transistor 128 will cause the collector 128c thereof toassume a relatively low voltage close to ground or common voltage. Thislow voltage will cause the base 13427 of transistor 134 to assume a lowvoltage below that required for transistor 134 to be triggered into theconduction state, thus causing transistor 134 to be turned off. Thevoltage at the collector 1340 will, therefore, rise toward the 13+ valueand will be communicated via resistor 122 to circuit location 118 whereit will trigger transistor 120 into the on or conduction state 'thusimposing a relatively low voltage signal at circuit port 126. Ashereinbefore stated, the presence of a low voltage signal at circuitport 126 will cause the selected injector valve means to open. When thevoltage signal from the manifold pressure sensor 12 has decayed to thevalue necessary for the multjvibrator to relax or return to its stablecondition, transistor 130 will be triggered on and transistor 128 willbe turned off. This will, in turn, cause transistor 134 to turn on,transistor 120 to turn off andthereby remove the injector control signalfrom circuit port 126.

During the period of time that transistor 134 has been held in thenonconducting, or off state, the relatively high'voltage at collector1340' has been applied to the base of transistor 136, triggering thetransistor 136 on." The resistor network 138, connected to the voltagesupply, acts with transistor 136 as a current source and current flowsthrough the conducting transistor 136 and begins to charge capacitor140. Simultaneously, transistor 142 has been biased on and, withresistor network 144, constitutes a second current source. Currents fromboth sources flow into the base of transistor 146 thereby holding thistransistor on which results in a low voltage at the collector 146c. Thislow voltage is communicated to the base of transistor 120 via resistor124.

When transistor 128 turns off signalling termination of the first pulsetransistor 134 turns on and the potential at the collector 1340 falls toa low value. The current from the current source comprised of transistor136 and resistor network 138 now flows through the base of transistor136 and the capacitor 140 ceases to charge. The capacitor will then havebeen charged, with the polarity shown in FIG. 2, to a valuerepresentative of the duration of the first pulse. However, at the endof the first pulse when transistor 134 is turned on the collector-basejunction of transistor 136 is forward biased, thus making the positiveside of capacitor 140 only slightly positive with respect to ground as aresult of being separated from ground by only a few pn junctions. Thiswill impose a negative voltage on circuit location 148 which willreverse bias diode 150 and transistor 146 will be turned off. This willinitiate a high voltage signal from the collector of transistor 146 tocircuit location 118 via resistor 124 which signal will re-triggertransistor 120 on and a second injector means control pulse will appearat circuit port 126. The time duration between the first and secondpulses wll be sufficiently short so that the injector means will notrespond to the brief lack of signal.

The duration of the second pulse will be a function of the time requiredfor circuit location 148 to become sufficiently positive for diode 150to be forward biased. This in turn is a function of the charge oncapacitor 140 and the magnitude of the charging current supplied by thecurrent source comprised of transistor 142 and resistor network 144. Thecharge on capacitor 140 is, of course, a function of the duration of thefirst pulse. However, the rate of charge (i.e., magnitude of thecharging current) is a function of the base voltage at transistor 142.This value is controlled by the voltage divider networks 152 and 154with the effect of network 154 being variably controlled by the enginetemperature sensor 14.

It has been determined that the amount of fuel injected and hence thepulse width of the injection pulses must vary for varying engine rpmvalues under constant load conditions. With reference to FIG. 2 the rpmcorrection is achieved by the circuitry enclosed by dashed line 200.Circuit 200 is operative to control the voltage applied to the secondarycoil 12s of pressure sensor 12. The voltage applied to the secondarycoil 12s is comprised of two components. The first component is providedby the voltage divider network comprised of parallel resistances 201 and202 coupled between B+ and the secondary coil 12s and diode 203 andresistance 204 going to ground. The second component, which is thevariable component, is established by the additional resistances 205,206 whose effect on the voltage at the secondary coil 12s is controlledby the conductivity of transistor 207. Transistor 207 is controlled inturn by circuitry which is responsive to the frequency of actuation ofthe monostable multivibrator (which is comprised of transistors 128 and130) and thus engine rpm. This control is achieved as follows:

Transistor 208 is normally conducting due to the voltage applied to itsbase by way of resistance 209, diode 210, and resistance 211interconnecting 8+ to ground. The current flowing therethrough will alsohave the effect of charging capacitor 212 up to a voltage valueintermediate B+ and ground by way of resistance 209 and resistance 213which is normally receiving a ground signal at collector 1300 oftransistor 130. However, whenever transistor 130 ceases to conduct, aswhen a trigger pulse is received at input port 1 16, the voltage atcollector 1300 will immediately go toward B+ and the charge acrosscapacitor 212 will adjust. When transistor 130 returns to the conductivestate, the voltage at collector 1300 will go to ground and the voltageapplied to the anode of diode 210 will go immediately to a value morenegative than the ground due to the capacitor action of capacitor 212and diode 210 will be reverse biased. This will, in turn, causetransistor 208 to be triggered off and the voltage appearing at thecollector of transistor 208 and terminal 214 will rise toward a B+value. Alternatively, terminal 214 could be located at the collector oftransistor 216 if the values of the elements associated therewith wouldpermit the generation of fixed duration pulses. The voltage acrosscapacitor 212 will immediately begin to readjust and the anode of diode210 will eventually become forward biased. By properly selecting theresistance and capacitive values, the time period during whichtransistor 208 is off may be established at a fixed value due to the RCtime constant of this network. For purposes of providing batterycorrection by way of lead 156, this time period is normally selected tobe l millisecond. As the provision of battery correction, as well as theremaining portion of circuit 200, forms no part of the presentinvention, its mechanism will not be herein discussed. As soon as diode210 becomes forward biased, transistor 208 will again turn on and thevoltage at the collector of transistor 208 will go substantially to theground potential. Thus, a pulse train of fixed width pulses will appearat circuit port 214 with a repetition rate directly indicative of enginespeed. The interpulse interval will also be directly related to enginespeed.

Referring now to FIG. 3 of the drawing, a circuit 300 according to thepresent invention and illustrative of a preferred embodiment thereof isshown. The circuit 300 is energized by B+ as noted and this may readilybe the same source of energization as is illustrated and discussed withregard to FIG. 2. Circuit 300 has an output port 302 and three inputports denoted as 214, 304,

and 306. Input port 214 corresponds to the similarly designated portillustrated in FIG..2 and discussed in relation thereto. In thisembodiment, circuit port 214 is communicated to base or first controlelectrode 308b of transistor 308 by resistive circuit means whichinclude resistances 310, 312, and 314, diode 316, and integratingcapacitor 318. The base 308b of transistor 308 is communicated to asource of voltage by resistance 320 and is also communicated to groundby resistance 322 and diode 324. In this embodiment, the resistance 320is connected to a source of regulated voltage illustrated as zener diode326 which is operative to establish a regulated voltage within commonconductor 328 which communicates the cathode of the zener diode 326 toresistance 330 which in turn is connected to the supply B-las shown. Thecollector of transistor 308 is coupled to the base 310!) of transistor310 through resistance 332 and the emit emitters of transistors 308 and310 are coupled together and coupled to ground by resistance 334. Thecollector of transistor 308 is connected to the common connector 328 byresistance 336 and the collector of transistor 310 is connected to thecommon conductor 328 by resistance 338. The collector of transistor 310is also coupled to the base 34% of transistor 340 through resistance341. Transistors 308 and 310, together with their respective load andlimit resistances form a Schmitt trigger and the resistive values aresuch that the Schmitt trigger will normally be biased with transistor308 in the off or nonconducting mode and transistor 310 in the on orconducting mode. The emitter of transistor 340 is connected byresistance 342 to the common conductor 328 and by resistance 344 to thecommon or ground location. Resistances 342, 344 form a voltage dividernetwork to establish a bias voltage at the emitter of transistor 340.The collector of transistor 340 is .directly coupled .tothe base 346boftransistor 346.and to the source of energization, B+, by resistance 348.While all other transistors in circuit 300 are illustrated as npntransistors, transistor 346 is shown as a pnp-transistor with itsemitter electrode connected to the source of energization, B+, and itscollector electrode connected to the output port 302 of the circuit 300.It should be noted, however, that transistor types .herein are merely amatter of designers choice.

' Base or second control electrode 310b of transistor 310 is connectedby way of resistance 350 and diode 352 to output port 306 which is alsocoupled to ground by diode 354. Diode 352 is connected so that itscathode is coupled to the output port 306 while its anoe, while coupledto resistance 350, is coupled to the 13+ supply by way of resistance356. Thus, in the absence of a low voltage signal at output port 306which would forward bias diode 352, resistances 336, 332, 350, and 356form a voltage divider network operative to establish the voltage at thebase of transistor 310 at some value intermediate the B supply voltageand the regulated voltage existing in common conductor 328. By suitablyarranging the resistive values, the Schmitt trigger can be so biasedthat transistor 310 is normally in conduction as hereinbefore stated.Circuit output port 306 may be coupled to throttle switch 38 (as shownin F IG. 1). The. circuit as hereinabove described is adapted to operatewhen actuation of switch 38 applies a ground or common low voltagesignal to a circuit port 306 to forward bias diode 352. Diode 354 asillustrated is operative to provide contact arcing protection.

Diode 358 interconnects circuit input port 304 with the base oftransistor 340 and is arranged to have its cathode connected directly toinput port 304. The cathode of diode 358 is also connected to the sourceof energy, B+, by resistance 360. Diode 362 interconnects input port 304with ground and is connected relative to diode 358 in acathode-to-cathode relationship. The presence of a very low voltagesignal at circuit input port 304 is operative to provide a very lowresistance path to ground from the base 340!) of transistor 340 so as toprevent the turn-on of that transistor under any and all operatingconditions. For instance, by coupling input port 304 to the vehicletransmission so that a ground signal appears whenever the transmissionis in park" or neutral, transistor 340 may be forced off and the circuitmay be inhibited. Resistance 360 provides noise protection for thisportion of circuit 300.

Input port 214 is also coupled to the base 362b of transistor 362 byresistance 364. The collector of transistor 362 is coupled to the commonconductor 328 by resistance 366 and interval determining means in theform of capacitor 368 are connected from the collector of transistor 362to the common or ground point. The emitter of transistor 362 is alsoconnected to ground so that interval determining means 368 are connectedacross the emitter and collector of transistor 362. The collector oftransistor 362 V is also connected to the anode of a bistable switch 370having a control electrode 372. The cathode of the switch is connectedto the base 310!) of transistor 310. The control electrode 372 iscoupled to the common or ground potential by a resistance 374 and bydiode 376 to a voltage divider comprised of resistances 378 and 380.Resistances 378 and 380 interconnect the common conductor 328 with thecommon or ground point and operative to apply a predetermined level ofvoltage to the gate or control electrode372 while resistance 374 isoperative to provide a current flow path to ground for current flow fromthe control electrode 372. Bistable switch 370 is herein illustrated asa programmable unijunction transistor (PUT). Such a device is operativeto switch from a nonconducting to a conducting state whenever thevoltage applied to the anode thereof exceeds the voltage applied to thecontrol electrode by the voltage drop across one pn junction (typically,7/10 of a volt). Once conducting, such devices will remain conductingfor any value of voltage applied to the gate, or'anode, until thecurrent flow through the device has dropped to a very low level.Bistable switching device 370 may also be a silicon controlled rectifier(SCR) and such devices are known to operate in substantially the samefashion as a PUT in this type of embodiment. Furthermore, other devicesof this general character may be utilized for bistable switching device370.

OPERATION Upon the application of an energizing supply, B+, as forinstance by way of an automotive ignition switch, regulating zener diode326 will operate to establish a regulated voltage in common conductor328. Since this voltage will be lower than the B+ voltage, a currentwill flow through resistor 356, resistance 350, resistance 332, andresistance 336 establishing a voltage at base 31012 of transistor 310which is intermediate the regulated voltage and the B+ supply voltage.By suitable sizing the resistors as hereinbefore stated, this voltage,relative to the voltage established at base 308b of transistor 308, canbe sufficient to cause transistor 310 to go into conduction therebyholding transistor 308 off. By suitably arranging the resistances 338and 334, the voltage at the emitters of transistors 308 and 310 can beestablished intermediate the regulated voltage and the ground level, andby suitably arranging the resistances 320 and 322 the voltage present atthe base 308b will be less than the voltage at the emitters. This willthen reverse bias the emitter base junction of transistor 308 and thistransistor will be held off. Assuming normal vehicle operation over theentire speed range of which the engine is capable, and further assumingthat input ports 304 and 306 do not receive a grounded signal,transistor 308 will be held off and transistor 310 will be held on sothat no base currentmay flow into' will be grounded and will thus causethe current flow through resistances 336, 332, and 350 to reverse indirection. This will cause the voltage applied to the base of transistor310 to drop to a value which is merely sufficient to maintain conductionthereof.

Normal operation of the FIG. 2 circuit will cause a sequence of pulsesto appear at terminal 214 thereof, as well as terminal 214 of the FIG. 3circuit, which pulses have a fixed duration and a repetition rate whichis directly indicative of the engine speed. The pulses received atterminal 214 of circuit 300 will be applied to the integrating capacitornetwork comprised of resistance 312 and capacitor 318, and the capacitordischarge network which includes diode 316, resistance 314, resistance322, and diode 324 going to ground. As the repetition rate of thesepulses increases, the average voltage appearing at the anode of diode316 will increase so that the voltage level is substantially directlyindicative of the engine speed. By suitably sizing the capacitor thisnetwork may be arranged sothat the voltage appearing at the base 3081)of transistor 308 will be sufficiently high to drive that transistorinto conduction when the engine speed is above a preselected rpm valueand throttle switch 38 is closed. Resistance 332 will cause conductionof transistor 308 to provide a lower impedance path to ground forcurrent flowing through resistance 336 thereby terminating base currentflow into the base 3l0b of transistor 310. This will rapidly switchtransistor 310 off thereby causing the voltage on the collector oftransistor 310 to rise and thereby applying an increased voltage to base340b of transistor 340. This will cause transistor 340 to go intoconduction so that a current flows through resistance 348, therebyapplying a voltage drop in the forward direction across the emitter-basejunction of transistor 346. This will cause transistor 346 to go intoconduction and thereby apply a high voltage signal at output terminal302. Since the circuit 110 of FIG. 2 is arranged to provide a fuelinjection command output pulse in the form of a low voltage signal atterminal126, a high voltage signal at terminal 302 may be coupledthrough suitable blocking diodes for instance, directly to terminal 126to thereby terminate the provision of fuel injection command pulses.

Closure at any time of the transmission park or neutral switch,operative to apply a ground signal at terminal 304, will short circuitbase 340b to ground, thereby terminating or preventing flow of basecurrent to transistor 340 causing that transistor to switch to, ormaintain an off condition and therefore causing transistor 346 to switchor maintain an off condition. Furthermore, an opening of switch 38operative to terminate the ground signal at port 306 during a fuelcutoff cycle will cause a base current to flow into base 31% by way ofresistances 356 and 350. The provision of this base current will causetransistor 310 to switch back on again and by the intercoupling ofemitters will concomitantly cause transistor 308 to rapidly switch off.This will also terminate the provision of a high voltage output signalat terminal 302. This, the fuel cutoff signal may be terminated byeither an opening of throttle switch 38 or a closure of the transmissionpark or neutral" switchf'l'he present invention therefore initiates fuelcutoff only when the speed of the engine is above a preselected valueand the throttle switch has been closed and, as an auxiliary condition,the transmission of the vehicle with which the engine is associated isnot in a park or neutral setting.

The receipt of the fixed pulse width pulses at terminal 214 will befurther operative to periodically cause transistor 362 to go intoconduction due to the receipt of a high voltage signal throughresistance 364 at base 362b. Transistor 362 will be in conduction for atime period which substantially corresponds, within the limits of solidstate electronic device switching times, to the width of the fixed widthpulse. When transistor 362 is nonconducting (i.e., during interpulseintervals), the regulated voltage from the common conductor 328 will beapplied through resistance 366 to capacitor 368. The capacitor 368 willtherefore charge to a value which is directly related to the interpulseinterval and hence to engine rpm. The periodic switching on oftransistor 362 will be operative to provide a voltage discharge path toground for capacitor 368 and by suitably sizing this capacitor, it canbe arranged to be fully discharged during the fixed pulse widthduration. Furthermore, by suitably sizing the resistance 366 the RC timeconstant of this resistance and capacitor 368 can be arranged to berelatively long compared with the discharge time so that the charge-uptime of the capacitor is of a comparatively long duration. Thus, whenthe interpulse interval is comparatively short, as, for instance, atrelatively high speed operation, the capacitor will be periodicallycharged'up to a low value. However, after a fuel cutoff signal has beengenerated at output port 302, the speed of the engine can be readilypresumed to be decreasing. Therefore, the voltage across capacitor 368and hence the voltage applied to the anode of bistable switching device370 will be somewhat higher for each successive interpulse interval.Resistances 378, 374, 380, and diode 376 form a voltage divider networkwhich establishes a fixed level of voltage at gate electrode 372. It cantherefore readily be arranged that, when'the engine speed reaches apredetermined value which may be, for instance, the curb idle speed, thevoltage accumulated across capacitor 368 during the next succeedinginterpulse interval will be sufficiently high (one diode drop above thevoltage applied to gate 372) so that bistable switching de vice 370 goesinto conduction. Once conducting, the current flowing therethrough willbe applied to the base of 31% of transistor 310 to cause that transistorto go into conduction. Conduction of that transistor will cause thetermination of conduction of transistor 340, the termination ofconduction of transistor 346, and the termination of the fuel cutoffsignal at output terminal 302. Thus, the present invention provides acircuit which can readily examine the operating speed of the engine bymeasuring a pulse width interval to determine when that interval hasreached a predetermined width so as to terminate fuel cutoff and therebyprevent stalling of the engine. By separating the high speed and lowspeed signaling circuitry, tailoring of the overall circuit to suitparticular applications and different systems and engines may be readilyaccomplished. The use of interval determining means 368 for low speedsignaling permits accurate low speed calculation so that the low speedstall point may be closely approached without danger of stalling theengine. Furthermore, by making throttle closure and attainment of thepreselected low rpm the positive switching criterion and the presence ofa high rpm signal a condition for switching, the determination ofcircuit element values for a multi-conditional responsive Schmitttrigger is greatly simplified.

Referring now to'FIG. 4, an alternate input stage is illustrated forthose situations when the voltage or energy level of the fixed widthpulse applied to terminal 214 is not sufficiently great to chargecapacitor 318 and to drive transistor 362 into conduction. As can beseen, this alternate circuit includes a transistor 380 whose emitter isconnected to ground through resistance 382 and also to the cathode of asecond voltage level regulating device, zener device 384, throughresistance 386. This input stage would otherwise be coupled to circuits300 as indicated by the commonlydesignated resistances 312 and 364. i

I claim:

1. In an internal combustion engine having a signalling device forsignalling an acceleration demand and a deceleration demand, and a fuelcontrol system of the signal, an improved deceleration fuel controlcircuit comprising:

a. an output switchhaving an output switch control electrode and anoutput switch output electrode connected to said computing means, saidoutput switch operative to provide at said output switch outputelectrode a normal fuel output level and a fuel cutoff output level,said normal fuel output level operative to permit said computing meansto normally generate said output signals and said fuel cutoff signaloperative to cause said computing means to generate output signalsreducing the fuel delivered to the engine;

b. a first control switch operative to control said output switch havinga first control switch output electrode connected to said output switchcontrol electrode and a first control switch control electrode connectedto said signalling device, said first control switch operative tonormally provide at said first control switch output electrode a firstcontrol switch first output level when said signalling device signalssaid deceleration demand and a first control switch second output levelwhen said signalling device signals said acceleration demand;

c. a second control switch for controlling said first control switchhaving a second control switch control electrode connected to said speedpulse generating means and a second control switch'output electrodeconnected to said first control switch control electrode, said secondcontrol switch being responsive to voltages at said second controlswitch control electrode to permit said first control switch to normallyprovide said first control switch second output level for second controlswitch control electrode voltages below a first predetermined speeddependent level when said signalling means signals said decelerationdemand so as to permit said output switch to provide said normal fueloutput level and to otherwise control said first control switch toprovide said first control switch first output level for control switchcontrol electrode voltages above said predetermined speed dependentlevel so as to control said output switch to provide said fuel cutoffoutput level;

d. a multiple-pulse interval-averaging capacitor connected to saidsecond control switch control electrode operative to provide a secondcontrol switch control electrode voltage indicative of an average of aplurality of said engine speed pulse intervals, said second controlswitch control electrode voltages varying with said repetition rate ofsaid speed pulses so as to control said second control switch to controlsaid first'control switch to provide said second output level forcausing said output switch to provide said fuel cutoff output levelwhenever said voltage provided by said multiple-pulse interval-averagingcapacitor exceeds said first predetermined engine speed dependentvoltage; and

e. inter-pulse interval computing means connecting said pulse generatingmeans and said first control switch control electrode for controllingsaid first control switch to provide said first output level so thatsaid output switch provides said normal fuel output level whenever aninterval between two successive pulses is indicative of an engine speedless than a second predetermined engine speed dependent level less thansaid first: predetermined engine speed dependent level, said inter-pulsecomputing means comprising a source of constant potential, a resistorand a computing capacitor connected in series to said source of constantpotential, a first discharge switch, a second discharge switch, andvoltage divider means, said first discharge switch having a firstdischarge switch control electrode connected to said pulse generatingmeans and a first discharge switch discharge electrode connectedintermediate said resistor and said computing capacitor operative todischarge said computing capacitor during each said fixed duration ofsaid fixed duration speed pulses, said second discharge switch having anoutput electrode connected to said first control switch controlelectrode, second discharge switch discharge electrode connectedintermediate said resistor and said computing capacitor, and a seconddischarge switch control electrode, said voltage divider means connectedintermediate said source of constant potential and said second dischargeswitch control electrode operative to provide thereat a second dischargeswitch control electrode voltage indicative of said second predeterminedengine speed dependent level, whereby said computing capacitor isdischarged through said second discharge switch to control said firstcontrol switch to provide said second output level whenever the intervalbetween successive speed pulses allows said computing capacitor tocharge from said constant potential source to a level above said secondpredetermined engine speed dependent level before being discharged bysaid first discharge switch.

2. In an internal combustion engine having a first signalling device forsignalling an acceleration demand and a deceleration demand, a secondsignalling device for signalling engine operation modes including a Parkmode and a Neutral mode, and a fuel control system of the type havingspeed pulse generating means responsive to engine speed operative togenerate a pulse train of fixed duration speed pulses having a pulserepetition rate varying directly with engine speed and an interpulseinterval varying inversely with engine speed, computing means operativeto generate an output signal indicative of engine fuel requirement, andinjector valve means actuable in response to the computing means outputsignal to control the fuel delivered to the signal, an improveddeceleration fuel control circuit comprising: 1

a. an output switch having an output switch control electrode connectedto said second signalling device and an output switch output electrodeconnected to said computing means, said output switch operative toprovide at said output switch output electrode a normal fuel outputlevel and a fuel cutoff output level, said normal fuel output levelbeing provided when said second signalling device signals one of saidPark and Neutral modes to normally permit said computing means tonormally generate said output signals and said fuel cutoff signaloperative to cause said computing means to generate output signalsreducing the fuel delivered to the engine;

b. a first control switch operative to control said output switch havinga first control switch output electrode connected to said output switchcontrol electrode and a first control switch electrode connected to saidfirst signalling device, said first control switch operative to normallyprovide at said first control switch output electrode a first controlswitch first output level when said first signalling device signals saiddeceleration demand and a first control switch second output level whensaid first signalling device signals said acceleration demand;

0. a second control switch for controlling said first control switchhaving a second control switch control electrode connected to said speedpulse generating means and a second control switch output electrodeconnected to said first control switch control electrode, said secondcontrol switch being responsive to voltages at said second controlswitch control electrode to permit said first control switch to normallyprovide said first control switch second output for second controlswitch control electrode voltages below a first predetermined speeddependent level when said first signalling means signals saiddeceleration demand so as to permit said output switch to provide saidnormal fuel output level and to otherwise control said first controlswitch to provide said first control switch first output level for thecontrol switch control electrode voltages above said predetermined speeddependent level so as to control said output switch to provide said fuelcutoff output level;

(1. a multiple-pulse interval-averaging capacitor connected to saidsecond control switch control electrode operative to provide a secondcontrol switch control electrode voltage indicative of an average of aplurality of said engine speed pulse intervals, said second controlswitch control electrode voltages varying with said repetition rate ofsaid speed pulses so as to control said second control switch to controlsaid first control switch to provide said second output level forcausing said output switch to provide said fuel cutoff output levelwhenever voltage provided by said multiple-pulse intervalaveragingcapacitor exceeds said first predetermined engine speed dependentvoltage; and

. single inter-pulse interval computing means conmeeting said pulsegenerating means and said first control switch control electrode forcontrolling said first control switch to provide said first output levelso that said output switch provides said normal fuel output levelwhenever the interval between two successive speed pulses is indicativeof an engine speed less than a second predetermined engine speeddependent level less than said first predetermined engine speeddependent level, said inter-pulse computing means comprising a source ofconstant potential, a resistor and a computing capacitor connected inseries to said source of constant potential, a first discharge switch, asecond discharge switch, and voltage divider means, said first dischargeswitch having a first discharge switch control electrode connected tosaid pulse generating means and a first discharge switch dischargeelectrode connected intermediate said resistor and said computingcapacitor operative to discharge said computing capacitor during eachsaid fixed duration of said fixed duration speed pulses, said seconddischarge switch having an output electrode connected to said firstcontrol switch control electrode, second discharge switch dischargeelectrode connected intermediate said resistor and said computingcapacitor, and a second discharge switch control electrode, said voltagedivider means connected intermediate said source of constant potentialand said second discharge switch control electrode operative to providethereat a second discharge switch control electrode voltage indicativeof said second predetermined engine speed dependent level, whereby saidcomputing capacitor is discharged through said second discharge switchto control said first control switch to provide said second output levelwhenever the interval between successive speed pulses allows saidcomputing capacitor to charge from said constant potential source to alevel above said second predetermined engine speed dependent levelbefore being discharged by said first discharge switch.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,809,028 Dated y 7 Inventor(s) D vid C. LUChEiCO It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In co1umn 13, h'rie 9, after the word "switch" insert --contr01---Signed and sealed this 17th day of September 1974.

1 (SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN T Attesting Officer Commissioner ofPatents DRM Pb-mso (10-69! USCOMM-DC 60376-P69 e u so ooynumzyr PRINTINGOFFICE I969 o3ss-a34

1. In an internal combustion engine having a signalling device forsignalling an acceleration demand and a deceleration demand, and a fuelcontrol system of the type having speed pulse generating meansresponsive to engine speed operative to generate a pulse train of fixedduration speed pulses having a pulse repetition rate varying directlywith engine speed and an interpulse interval varying inversely withengine speed, computing means operative to generate an output signalindicative of engine fuel requirement, and injector valve means actuablein response to the computing means output signal to control the fueldelivered to the signal, an improved deceleration fuel control circuitcomprising: a. an output switch having an output switch controlelectrode and an output switch output electrode connected to saidcomputing means, said output switch operative to provide at said outputswitch output electrode a normal fuel output level and a fuel cutoffoutput level, said normal fuel output level operative to permit saidcomputing means to normally generate said output signals and said fuelcutoff signal operative to cause said computing means to generate outputsignals reducing the fuel delivered to the engine; b. a first controlswitch operative to control said output switch having a first controlswitch output electrode connected to said output switch controlelectrode and a first control switch control electrode connected to saidsignalling device, said first control switch operative to normallyprovide at said first control switch output electrode a first controlswitch first output level when said signalling device signals saiddeceleration demand and a first control switch second output level whensaid signalling device signals said acceleration demand; c. a secondcontrol switch for controlling said first control switch having a secondcontrol switch control electrode connected to said speed pulsegenerating means and a second control switch output electrode connectedto said first control switch control electrode, said second controlswitch being responsive to voltages at said second control switchcontrol electrode to permit said first control switch to normallyprovide said first control switch second output level for second controlswitch control electrode voltages below a first predetermined speeddependent level when said signalling means signals said decelerationdemand so as to permit said output switch to provide said normal fueloutput level and to otherwise control said first control switch toprovide said first control switch first output level for control switchcontrol electrode voltages above said predetermined speed dependentlevel so as to control said output switch to provide said fuel cutoffoutput level; d. a multiple-pulse interval-averaging capacitor connectedto said second control switch control electrode operative to provide asecond control switch control electrode voltage indicative of an averageof a plurality of said engine speed pulse intervals, said second controlswitch control electrode voltages varying with said repetition rate ofsaid speed pulses so as to control said second control switch to controlsaid first control switch to provide said second output level Forcausing said output switch to provide said fuel cutoff output levelwhenever said voltage provided by said multiple-pulse interval-averagingcapacitor exceeds said first predetermined engine speed dependentvoltage; and e. inter-pulse interval computing means connecting saidpulse generating means and said first control switch control electrodefor controlling said first control switch to provide said first outputlevel so that said output switch provides said normal fuel output levelwhenever an interval between two successive pulses is indicative of anengine speed less than a second predetermined engine speed dependentlevel less than said first predetermined engine speed dependent level,said inter-pulse computing means comprising a source of constantpotential, a resistor and a computing capacitor connected in series tosaid source of constant potential, a first discharge switch, a seconddischarge switch, and voltage divider means, said first discharge switchhaving a first discharge switch control electrode connected to saidpulse generating means and a first discharge switch discharge electrodeconnected intermediate said resistor and said computing capacitoroperative to discharge said computing capacitor during each said fixedduration of said fixed duration speed pulses, said second dischargeswitch having an output electrode connected to said first control switchcontrol electrode, second discharge switch discharge electrode connectedintermediate said resistor and said computing capacitor, and a seconddischarge switch control electrode, said voltage divider means connectedintermediate said source of constant potential and said second dischargeswitch control electrode operative to provide thereat a second dischargeswitch control electrode voltage indicative of said second predeterminedengine speed dependent level, whereby said computing capacitor isdischarged through said second discharge switch to control said firstcontrol switch to provide said second output level whenever the intervalbetween successive speed pulses allows said computing capacitor tocharge from said constant potential source to a level above said secondpredetermined engine speed dependent level before being discharged bysaid first discharge switch.
 2. In an internal combustion engine havinga first signalling device for signalling an acceleration demand and adeceleration demand, a second signalling device for signalling engineoperation modes including a Park mode and a Neutral mode, and a fuelcontrol system of the type having speed pulse generating meansresponsive to engine speed operative to generate a pulse train of fixedduration speed pulses having a pulse repetition rate varying directlywith engine speed and an inter-pulse interval varying inversely withengine speed, computing means operative to generate an output signalindicative of engine fuel requirement, and injector valve means actuablein response to the computing means output signal to control the fueldelivered to the signal, an improved deceleration fuel control circuitcomprising: a. an output switch having an output switch controlelectrode connected to said second signalling device and an outputswitch output electrode connected to said computing means, said outputswitch operative to provide at said output switch output electrode anormal fuel output level and a fuel cutoff output level, said normalfuel output level being provided when said second signalling devicesignals one of said Park and Neutral modes to normally permit saidcomputing means to normally generate said output signals and said fuelcutoff signal operative to cause said computing means to generate outputsignals reducing the fuel delivered to the engine; b. a first controlswitch operative to control said output switch having a first controlswitch output electrode connected to said output switch controlelectrode and a first control switch electrode connected to said firstsignalling device, said first control switch operative to normallyprovide at said first control switch output electrode a first controlswitch first output level when said first signalling device signals saiddeceleration demand and a first control switch second output level whensaid first signalling device signals said acceleration demand; c. asecond control switch for controlling said first control switch having asecond control switch control electrode connected to said speed pulsegenerating means and a second control switch output electrode connectedto said first control switch control electrode, said second controlswitch being responsive to voltages at said second control switchcontrol electrode to permit said first control switch to normallyprovide said first control switch second output for second controlswitch control electrode voltages below a first predetermined speeddependent level when said first signalling means signals saiddeceleration demand so as to permit said output switch to provide saidnormal fuel output level and to otherwise control said first controlswitch to provide said first control switch first output level for thecontrol switch control electrode voltages above said predetermined speeddependent level so as to control said output switch to provide said fuelcutoff output level; d. a multiple-pulse interval-averaging capacitorconnected to said second control switch control electrode operative toprovide a second control switch control electrode voltage indicative ofan average of a plurality of said engine speed pulse intervals, saidsecond control switch control electrode voltages varying with saidrepetition rate of said speed pulses so as to control said secondcontrol switch to control said first control switch to provide saidsecond output level for causing said output switch to provide said fuelcutoff output level whenever voltage provided by said multiple-pulseinterval-averaging capacitor exceeds said first predetermined enginespeed dependent voltage; and e. single inter-pulse interval computingmeans connecting said pulse generating means and said first controlswitch control electrode for controlling said first control switch toprovide said first output level so that said output switch provides saidnormal fuel output level whenever the interval between two successivespeed pulses is indicative of an engine speed less than a secondpredetermined engine speed dependent level less than said firstpredetermined engine speed dependent level, said inter-pulse computingmeans comprising a source of constant potential, a resistor and acomputing capacitor connected in series to said source of constantpotential, a first discharge switch, a second discharge switch, andvoltage divider means, said first discharge switch having a firstdischarge switch control electrode connected to said pulse generatingmeans and a first discharge switch discharge electrode connectedintermediate said resistor and said computing capacitor operative todischarge said computing capacitor during each said fixed duration ofsaid fixed duration speed pulses, said second discharge switch having anoutput electrode connected to said first control switch controlelectrode, second discharge switch discharge electrode connectedintermediate said resistor and said computing capacitor, and a seconddischarge switch control electrode, said voltage divider means connectedintermediate said source of constant potential and said second dischargeswitch control electrode operative to provide thereat a second dischargeswitch control electrode voltage indicative of said second predeterminedengine speed dependent level, whereby said computing capacitor isdischarged through said second discharge switch to control said firstcontrol switch to provide said second output level whenever the intervalbetween successive speed pulses allows said computing capacitor tocharge from said constant potential source to a level above said secondpredetermined engine speed dependent level before being discharged bysaid first discharge switch.